Investigation of Liquid Dopants for the Production of High Efficiency Solar Cells from Dendritic Web Silicon

Abstract

Conventional gaseous BBr3 and CVD SiO2 are presently used in the Westinghouse baseline process for the production of high efficiency (13%–15%) dendritic web solar cells. The objective of this study was to replace the CVD SiO2 mask and the subsequent BBr3 diffusion step with a liquid SiO2/normalliquid boron dopant diffusion process. The number of process steps are reduced significantly with the use of the liquid process. Data on time‐temperature relationship on sheet resistance, junction depth, etc., were obtained and are presented. Various application techniques for the liquid process were investigated. As a first step, a manually applied sponge‐squeegee applicator was used, which was later replaced with a meniscus coating machine. This equipment permitted the application of uniform layers of liquid dopants of controlled thickness on the dendritic web. Various runs were made to make direct comparison of the liquid and baseline processes. The results of cell efficiencies achieved using the liquid process indicate that high efficiencies (13%–15%) can be achieved with this process. Results of VOC , ISC , fill factor, etc., are presented in detail and compared with the baseline process. Dark IV measurements made on liquid‐processed cells indicate excellent quality junctions and high lifetime values. The series and shunt resistance measurements on typical cells show no difference as compared with the baseline process. Junction profiles are presented for both a gaseous diffused cell and a liquid processed cell. The profiles show no dissimilarities.

Silicon ultrafast recovery diode with leakage current reduced via the combined lifetime process of gold diffusion and electron-beam irradiation

“…However, this method significantly increases the leakage current [18]. In contrast, there is another method to control the lifetime of minority carriers by forming defects via electron-beam or particle ion-beam irradiation [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37], and the physical and electrical characteristics of the defects have been investigated [38][39][40][41][42][43][44][45][46]. The leakage current can be reduced to less than that of a solely Au-diffused diode by generating defects via electron-beam irradiation (EI) [47].…”